Internal combustion hammer



Feb. 17, 1942.

m ll;

C. E. FITCH 2,273,095

INTERNAL COMBUSTION HAMMER Filed Aug. 11, 19:59 3 Sheets-Sheet 1 7 BY r I I 406211 5/ ATTORNEY Feb. 17, 1942. c, cH v 2,273,095

INTERNAL COMBUSTiON HAMMER Filed Aug. 11, 1959 3 Sheets-Sheet 2 INVENTOR C/l'ffo/"o E. F/7c/1.

fl ML ATJI'ORNEY Feb. 17, 1942.

c. E. FITCH 2,273,095

INTERNAL COMBUSTION HAMMER Filed Aug. 11, 1939 3 Sheets-Sheet 3 INVENTOR. C/if/ora E. F/fc/z.

BY WORNEY I position of. the wor impact is not always the same 'I'he return Patented Feb. 17,

UNITED STATES PATENT OFFICE" m'rnnnanconmus'rrorinamvmn Clifford E. men, Cleveland, Ohio, minor to,

Chicago Pneumatic Tool Company, New York, N. '1', a corporation otNcw Jersey V Application Augean, iaaaseriai No. 2 89,54!

1Claim.

by relative movement 'of the cage, to deliver a blow upon a working implement such as a drill steel or tamping bar.- Hammer assemblies of this type have been used heretofore chiefly in electrically operated tools, and it is thought that the present invention, in one of its broad aspects, resides in the'combination of an internal combustion engine with a hammer assembly of the type described.

The invention has a particular reference .to the use of a free hammer piston with. a two-cycle internal combustion engine of the double acting type; namely, one that has a single driving piston and an explosion or combustion chamber adjacent each endgof the. driving pis ton. A double acting engine has many. advantages over the single acting type, but'the principal advantage is gained by the elimination of the usual quent replacementdue to breakage and, moreover, reduces the efliciency and power of the engine by absorbing energy when compressed during the power stroke ofthe piston.

While the advantages of the double acting implement with non yielding engagement. In

such an arrangement, the length of stroke of the piston is not uniform due to the fact that the g implementat the time of spring permits such variations in length of stroke. On the other hand, the use, in adouble acting engine, of ignited gas to return the piston, in

place of the spring that characterizes the single acting type, necessitates a substantially uniform length of piston stroke, since the explosion in the lower chamber must betimed to occur at :a fixed point in the operation of the machine. A

if timing mechanism is regulated for a; short stroke the ior'ce of blow is frequently too' weak,

free piston type of double acting engine with a uniform piston stroke will not produce the best results if the piston is re- 'quired to strike the implement directly, because whereas, the selection of a relatively long stroke might result in stalling the engine whenever the position of the working implement happened to -be unusually high. According to the present invention, this defect is remedied by the use of a free piston hammer assembly, wherein the cylindrical cage is directly connected tothe driving or engine piston of uniform stroke and the hammer piston moves through a variable range of i0 movement, within the cage, to strike .the working implement.

One object of the invention is to increase the, efliciency and adaptability of a percussive toolby,

associating, in combination, an internal combustion engine and a free piston type hammer asg driving piston to a working implement through an intermediate hammer. assembly which includes a hammer piston having a variable range of movement.

Other objects and structural details of the. in-

5 vention will be apparent from the following description when read in conjunction with the'accompanying drawings wherein:

Fig. 1 is .a longitudinal section through a tie' temper embodying the mechanism of the invention, e driving piston being in its uppermost spring for returning the driving piston through its compression stroke. Thisspring requires freposition, certain of the ignition apparatus being shown schematically; V Fig. 2 is an enlarged view of the upper section of- Fig. 1; I

.35 Fige3 is a view similar to Fig. 2, showing the driving piston indescending position;

Fig. 4 is an enlarged view of the lower section of .the tool, showing the hammer assemblyindescendingposition; Q I

Fig. 5 is a view similar to Figs. 2 and 3, showing the driving piston at the end of its descending stroke;

. Fig. 6 is a view similar to Fig. 4, but showing the hammer assembly at the time that the driving piston is; at the end of its descending stroke;

For purposes of description the tool maybe considered as consisting of two cooperating sections which form the opposite, or upper and lower, ends of the tool. The upper end of the tool is constructed as an internal combustion engine and the lower end as a support and guide for the impact delivering elements. As shown in Fig. 1, the-chief. supporting elements of the tool are a pairof cylinders 8 and 9, at the upper end, and a downwardly extending barrel Lat the lower end. Movable within the'cylinders 8 and 9 is a driving piston liformed with a connection rod l2 which extends downward into the barrel II and rigidly connects the piston to a cylindrical lower end of the barrel I and by an extension l6 secured to the barrel by bolts H. A bushing l8 for the bar I is supported inside the extension |6 at its lower end. In order to limit the downward movement of the tamping bar and to lessen the shock of the impact delivered thereon, a cushioning assembly is positioned atop the bushing l8. This assembly comprises a cushion l9 made of rubber or similar material, a retaining ring 2| and a contact disc 22 which restson the upper end of the cushion in position to be engaged by the lower surface of a shoulder 23 formed on the bar .|5. To limit the movement of the bar in the opposite, or upward, direction,

Considering now the internal combustion entime and referring to Fig 2 it willbe noted that the two cylinders 8 and 9 are secured together by bolts 25 and that the lower cylinder 9 is fixed to the upper end of the barrel l0 by means of bolts 26. The cylinders 8 and 9 are so connected that the respective explosion chambers 21 and 28 are aligned and form, in effect, a single chamber in which the driving piston reciprocates.

Opening into explosion chambers 21 and 28 are passageways 29 and 3| respectively, by which a compressed charge of gasoline laden air is introduced into the combustion chambers. Respecthe present arrangement of two metering valves may be retained.

In considering the operation of the engine it may be assumed that, in Fig. 2, the piston II has just been driven upward by an explosion in the lower chamber 28 and a compressed charge is trapped in the upperchamber 2'l ready to be a spacing ring is placed within the barrel Hi above the shoulder 23.

tive exhaust ports 32 and 33 are also provided in each combustion chamber to permit the escape of burned gases. Communicating withthe passageways 29 and 3|, by means of ports 34 and 35; is a pre-compression chamber 36 closed by the piston A piston head 38, formed midway along the driving piston, has a sliding fit with the bore of chamber 36 and divides it into upper and lower compartments. Separate valves 39 and 4| contained in respective housings 40 and 42 are provided for controlling the flow of the explosive mixture into .the passageways 29 and 3|. These valves are alike and a description of the construction and operation of one will suffice for both. The valve is of the poppet type and is urged by a spring 43 into the position shown-in Fig. 2 where it acts to close the valve opening '44 leading into a passageway 29 or 3|. Access to atmosphere is obtained through the valve housing by means of ports 45, and gasoline is directed to the valve openingfrom a tank (not shown) through a passage 46 com- 'municating with inlet 41; A set screw or metering valve 48 is provided for regulating the now of liquid fuel through'passage 46. The valves 39 and 4| have been shown in their present positions principally to :mplify the disclosure. In the actual construction of the machine the valves may occupy the positions shown buta preferred arrang'ementis to have the valves side by side and approximately from the positions shown.

ignited by a spark from a plug 49 extending into the upper end of the chamber 21. When the explosion occurs in chamber 21 the piston II is driven downwardly. to seal the passageway 3| and exhaust port 33, from the lower chamber 26,

to'unseat this valve and thereby permit an explosive mixture to enter. passageway 3| and pros ceed in the direction of the arrows in Fig. 3 into the upper pre-compression chamber 36. As the piston continues to descend it uncovers first the exhaust port 32 in the upper chamber 21 and then the inlet from passageway 29. Thus at approximately the same time the burned gases escape through port 32 at one side of Chamber and a fresh mixture enters the chamber from itsopposite side. A projection 5| is formed on each end of the piston H and acts as a deflector to send the fresh gas toward the end of the combustion chamber and. away from the exhaust port. The movement of the gases at this time is indicated by the arrows in' Fig. 5 wherein the piston is shown in its extreme downward position just prior to the ignition of the compressed charge in chamber 28 by a plug 52 extending into the lower end of this chamber. The charge now in chamber 28 was introduced therein during the previous upward stroke of the piston As the piston II is driven upwardly the operation described above is repeated but reversed. That is, during this stroke, the mixture previously admitted to upper chamber 36 is compressed by movement of piston head 38 and when passageway 3| is uncovered this mixture enters the chamber 28 as the burned gases'escape therefrom through port 33. As the same time a partial vacuum is being created in lower chamber 36, thereby causing the poppet valve 39 to open and admit a fresh mixture into this chamber and passageway 29 which has been scaled by upward movement of the driving piston. By reason of the above arrangement, the piston II is given a positive reciprocating motion and the effect obtained is that of two engines-operating upon a single piston with each engine functioning on the basis of two strokes for one cycle. 1/

The ignitionsystem used in conjunction with the engine may be energized from an outside source such as a battery 53 (Fig.2) Individual coils C--| and C--2 are connected'to the respective spark plugs 49 and 52 and have a common respectively to contacts 54 and 55 engageable with an'armature 56 connected directly to the positive terminal of the battery. The armature In the latter construction a single metering. valve 48, common to both valves, may be used, al-

though if it should be found desirable to burn a richer mixture in one chamber than the other,

56, is in the form of a bell crank lever and is adapted to pivot about 'an axis 51 to engage one or the other of the contacts 54 and 55 to close the circuit through a coil C-I or 0-2 and cause a spark between the points of plug 49 or 52. A pair of oppositely disposed springs 58 and 59, connected to lever 58 above it pivot point 51, tend to centralize the lever in a position intermediate the contacts 54 and 55 to maintain the circuit through both coils normally open. The lever 55 is arranged for cooperation with a stud 6| fixed to the cylindrical cage I3, which stud may,'if desired, be formed as an extension on a wrist pin 62 which passes through the upper end of th cylindrical cage I3 and the lower end of connecting rod I2 to efiect a rigid connection between the cage and the driving piston II. The stud 6| projects through a longitudinal opening 60 cut in the barrel I0. The edge of the lever 55 which engages the stud 6| is formed with separate inclined surfaces 55Aand 563 which converge to a low point adjacent the pivot point 51. Thus, with the driving piston 'II in its upper position as shown in Fig. 2, the stud 6| engages the upper end of inclined surface 56A to hold the lever 56 rocked against the tension of spring 58 to close the circuit through coil C'-I to plug 49 and cause an explosion in upper chamber 21. Now, as the driving piston descends, the stud 6| moves downward along surface 56A and, as it approaches the mid-way point shown in Fig. 3,

moves out of engagement with the lever and allows the spring. 58 to centralize the lever and open the circuit. Continued downward movement of the piston causes the stud 5| to engage inclined surface 553 and, as the piston reaches its Fig. 5 position, the lever 55 is rocked in a clockwise direction to engage contact 55 and establish a circuit through coil C2 to spark plug 52 and cause an explosion in lower chamber 28. Return movement of the piston will, of course, cause a counter-clockwise movem'entof the lever 56 resulting in another explosion in the upper chamber 21. The timing mechanism thus operates under the the control of the cage I3 to cause explosions alternately in the chambers 21' and- 28.

Any suitable means may be used to start the engine. One such means is .shown here and comprises a manually operable plunger 63 extending downward through the upper end of the cylinder 8 and into the chamber 21. The lower end of plunger 63 is formed with a pin 63a (Fig.

7) adapted to be inserted in a bayonet slot 64 in the top surface of the upper projection 5|. The

its lower end, and is normally positioned on a seat 61 formed in the cylinder 8 to age from the explosion chamber 21.

Referring'now to Figs. 1, 4 and 6, the hammer assembly comprises,'as before mentioned, the cylindrical cage I3 and the hammer piston I4 positioned within the cage and movable relatively thereto. The principle of free piston hammers is old and well known in the art and a variety of practical embodiments thereof may be produced. The patent to C. B. Coates No. 1,191,948,

prevent leakissued July 25, 1916, shows a hammer assembly similar to that disclosed herein. The cage I3 is formed with shoulders 68 which engage the inner surface of the barrel III to hold the cage against lateral movement as it reciprocates with the driving piston II. formed with a head fitting snugly against the inner wall of the cage, and a stem or extension which passes through the lower end of-the cage in position to strike the tamping bar I5. The cage I3 is closed at its upper end and sealed at its lower end by the passage of the hammer piston I4 therethrough. A slot or slots 68, slightly longer than the head of hammer piston I4, are cut in the cage at its mid point in order that the mean pressures on opposite ends of the piston head may be approximately equal to each other and to atmospheric pressure. The upper and lower ends of the cage form respective air cushions or chambers II and 12. A the cage descends relative to the hammer piston the air in upper chamber II is compressed and drives the piston I I downward to strike the bar I5. In the up,- ward movement of the cage relative to the hammer piston the air in lower chamber. I2 is compressed and tends to return the piston to ,its Fig. 1 position, During the initial downward movement of the cage the. piston I4 first completes its upward movement, and then starts down but, due to its inertia, ata slower instantaneous speed than the cage I3. Until the speed of the piston I4 overtakes that of the cage, the size of the air pocket II decreases, as will be apparent from a comparison between Figs. v2 and 4. During the latter part of the downward stroke of the cage, the compressed air in pocket H expands, causing the hammer piston to move at a much greater speed than the cage I3. At the time the hammer piston I 4 strikes the bar I5,

it is moving independently of the cage I3 and the cage may start its return movement at the time of or slightly before the impact, without materially lessening the efiectiveness of the blow delivered by the piston.. In Fig. 6, the hammer piston has hit the bar I5 and rebounded slightly and the cage I3 is in itslowermost position.

It is possible to produce embodiments of the invention other than the one shown herein and it is intended that only such limitations shall be imposed upon the invention as are definedin the appended claim. Moreover, the illustrative embodiment is susceptible of other uses than described herein, as the hammer may be used to strike working implements other than tamper bars, for example drill steels.

What is claimed is:

An internal combustion hammer, comprising a cylinder having a combustion chamber formed at each end thereof, a hammer barrel secured to one end of said cylinder and axially aligned therewith, a working tool supported at the outer end of said hammer barrel, a .driving piston reciprocable within said cylinder, a hammer assembly within said barrel'including a reciprocable cylindrical cage and a floating piston therein arranged to deliver impacts to said working tool, an ignition system including a contact element adapted when set in one position to cause an explosion in one of said combustion chambers I and when set in another position to cause an explosion in the other of said combustion chambers, a connection between said driving piston and said cylindrical cage, and means comprised CLIFFORD E. FITCH.

The hammer piston I4 is' 

